There are numerous different security technologies on the market today to limit access to digital information and for physical security on doors or gates. One common method of limiting access to specific areas in a building includes iris recognition systems. These are the systems that scan a person's eyes to determine their identity and allow them access to restricted areas.

Since the early days of iris recognition technology, users and developers have assumed that the iris doesn't change over time. If the iris doesn't change over time that means a person can be enrolled once and the system should recognize them indefinitely. However, recent studies have shown that the iris of a person's eye can in fact change over time leading to the possibility of false negatives and false positives.

"The biometric community has long accepted that there is no 'template aging effect' for iris recognition, meaning that once you are enrolled in an iris recognition system, your chances of experiencing a false non-match error remain constant over time," stated Kevin Bowyer, Notre Dame's Schubmel-Prein Family Chair in Computer Science and Engineering.

"This was sometimes expressed as 'a single enrollment for life.' Our experimental results show that, in fact, the false non-match rate increases over time, which means that the single enrollment for life idea is wrong."

Bowyer worked with Sam Fenker, an undergraduate from Notre Dame, to analyze a very large data set containing iris images acquired over a longer period of time. The researchers were able to analyze iris images year to year for three successive years to determine if changes occurred. The research found that the iris could in fact change over time requiring reenrollment.

Bowyer added, "I do not see this as a major problem for security systems going forward… In the long run, researchers may develop new approaches that are 'aging-resistant.' The iris template aging effect will only be a problem for those who for some reason refuse to believe that it exists."